This invention relates to an electronic musical instrument, and more particularly a power supply circuit thereof.
For electronic musical instruments two types of power sources have been used, one a commercial AC source and the other a DC power source or a battery. In each type, the electronic musical instrument is constructed such that when a key is depressed after closing a source switch, a musical tone corresponding to the depressed key is produced. In such an electronic musical instrument, the performer often fails to open the power source switch after finishing the performance. This causes loss of power of a battery especially in a portable electronic musical instrument utilizing the battery as the power source. In the portable electronic musical instrument, unless the power consumption during performance is limited, the life of the battery will be shortened. This requires frequent renewal of the battery or use of a battery of a large capacity, so that use of a large battery increases the size and weight of the electronic musical instrument which makes it inconvenient to transport the same.